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1500HD 4X4 6.0L Gas Mileage

bubbatruckbubbatruck Member Posts: 2
edited March 2014 in Chevrolet
I purchased a 2002 1500HD 4X4 in July of this year. I got 7MPG with the first two tanks of gas. I returned it to the Dealer for service. They found a calibration fault in the computer. After fixing the fault I got 10MPH (city). I took it back to the dealer and was told nothing could be done until it had about 3000 miles on it. OK. I took a 400 mile trip pulling a trailer with 2 ATV's on it and got 10MPG. I have dueled the exhaust with 2 FloMasters and 3" pipe out the back. I have installed a K&N air filter and still only get between 11 - 12MPG city. I do not have a heavy foot or make allot of quick start and stops. So I would have to say that I am very dissapointed in the gas mileage of the 6.0L engine.


  • ryanbabryanbab Member Posts: 7,240
    You sound lucky

    Last tank of gas i got 11.2 on my 5.3 ext cab 4wd.

    I dont mean to sound like a smart @$$ but why did you buy a truck if your worried about low mpg? I do agree the 7 is low (dont get me wrong). Its a 6 liter V-8 the mpg isnt going to be that of a sedan with a 4 banger
  • kg11kg11 Member Posts: 530
    I get less than 9 (city) with my 8.1 and on the road ,less than 14.

    What's your hwy milage? I'm guessing about 15?

  • akjbmwakjbmw Member Posts: 231
    '98 K1500 5.7 AT ExtCab SB 3.73 with Fiberglass shell and Toyo Wild Country LT265s. Average about 14-15 city and 16-17 highway. In town I am the old man in the truck who is always in your way when you are in a hurry and the bumper in your rearview if you're lolligaggin'. On the highway, I have trouble keeping it from going over 80. ;-)
  • bubbatruckbubbatruck Member Posts: 2
    I understand what all of you are saying. I did not expect to get 19MPG out of this truck. I was expecting about 14 without the K&N air filter or deuling the exhaust. This is based on what I have read from others.
  • abedulerabeduler Member Posts: 5
    How is the 1500HD's 4L80-E differ from the 1500's 460? Will that affect mpg?

    I just bought one yesterday and will see what the gas is, that is what I'm worried about.

    Will the split exhaust help? How about performance chips? Tonneau cover?
  • obyoneobyone Member Posts: 7,841
    1500HD is actually a 2500LD. Being that its a heavier truck than the 1500, mileage will be affected. whether its a 2wd or 4wd also impacts weight, therefore, mileage along with driving style. Probable average 3-4 pg less than a 2wd 1500.

    I wouldn't expect much in terms of mpg increase with dual exhaust, chip, or tonneau cover even if they claim they do.
  • ryanbabryanbab Member Posts: 7,240
    Ive seen a 0.5-1mpg increase with my gm soft rollup cover
  • mledtjemledtje Member Posts: 1,123
    Seems to vary from truck to truck.

    My friend Vince and I have similar 2500 4x4 Reg Cab Longbed trucks. His has an automatic, mine has a 5 speed. He gets around 11 mpg. With a slide-in camper, and weighing 7440# mine gets around 14. Both are bone stock (well, Vince has slightly oversize wheels and tires) and run well.

    My worst tank has been around 10 and my best tank has been 16. Without the camper, I would expect around 17mpg. Sounds like I was lucky and go one of the trucks that returns good mileage.

    Mike L
  • abedulerabeduler Member Posts: 5
    My fears are true. With 700 miles on my new 4 door 1500HD, I got 12 mpg on my last tank with most of them highway miles!!! I'm not used to that with chevys.

    Remedy: I got a model 70 series Flowmaster on it and will see how that changes things. I want to change just one variable each time to see which has the most effect.

    The muffler sounds GREAT, and I'm very impressed with the improved performance....That really blows my mind how a muffler can add that much HP.

    Do any of you have better mpg the more miles you put on your engine? Am I being too anal?
  • obyoneobyone Member Posts: 7,841
    My mileage decreased with the addition of a catback.
  • abedulerabeduler Member Posts: 5
    Great!!! I was told it would DECREASE mileage... I'll see.

    I can't quantify the increase in HP, I can just tell a difference in pickup from stopped. And can really tell a difference when driving around 50-60 and increasing to 70+ while passing.

    I heard after installing a catback system, the person would unhook the battery to let the computer "reset" itself to adjust to the less restrictive flow.... I wonder if that's the deal? I have'nt done it myself, just wondering if you've done it or have heard of it.
  • lariat1lariat1 Member Posts: 461
    More than likely you will lower your MPG with a less restrictive exhaust, this is mostly due to to the fact that to make more power you need 2 things more fuel and more air, if you get more air the computer will adjust itself to keep emissions at thier programmed values. My experience has been that to increase MPG the only thing that works is either a tonneau cover or camper shell.
  • marcossmarcoss Member Posts: 1
    I have a '02 1500HD 4 x 4, Crew Cab, 6.0L, w/377 axle(I think). I'm running 33" Goodyear M/T. I have installed a Hypertech Power Programmer. I currently get about 10-11 MPGs. That's mostly driving about 30 miles a day in Houston Freeway traffic ( a lot of 0-60mph). I was thinking of adding these three items: 1)headers, 2)dual exhaust, and 3)K&N Filter Charger. That is until I read all these postings. I don't really want to lower my gas milage, but I do want to increase performance. Of these three options, which will give me the best performace and the lowest gas milage loss?

    Lastly, in response to "ryanbab", just because we own trucks, doesn't mean we should not be concerned about our gas milage. I would have expected 9-10 MPG our of a Ford V-10, but certainly did not expect it from my Chevy.
  • obyoneobyone Member Posts: 7,841
    A lot of the decrease in mileage can be attributed to the nice tone of an aftermarket exhaust and the desire to hear it once too often.

    To maximize performance, I recommend that all three mods you're listed be done. If I had to rate them, I'd do the following. A good catback system (not necessarily dual exhaust) as too much loss of back pressure will result in loss of power on the low end. Second a set of long tube headers. Shorty headers are only effective at high rpms. And a K&N FIPK, in that order.

    One of the mods that's often overlooked since its not a bolt on is changing gears. Very cost effective from the $ per HP gain. If you have the 3.73 and want a little more zip, consider changing to 4.10 cause those 33" have probably rendered your 3.73 to a 3.42.
  • ryanbabryanbab Member Posts: 7,240
    33s and 3.73 = a 3.60 rear end (based on 285s on stock 16x7 rims)
  • finns1finns1 Member Posts: 2
    Does anybody know the gas mileage on 1500 HD 2wd
    6.0 is?
  • truckluvertruckluver Member Posts: 11
    I get around 11 miles city and 13-14 miles highway.Not the best around, but what do you expect from a heavy duty truck with a large v-8?
    I guess I would get better milage if I were lighter on the pedal, but thats hard to do with this truck. Aside from the ticking, knocking from the engine and loose feeling in the steering wheel,it a fun truck to drive.
  • lspangler1lspangler1 Member Posts: 68
    My truck only has 250 miles on it and it's averaging just over 11 mpg with mixed city and highway.
  • chevydogchevydog Member Posts: 2
    Just checked my first tank and recorded 13.0 mpg in town driving with the last 40 miles pulling a trailer loaded with firewood...not bad
  • zionalbinozionalbino Member Posts: 2
    I bought this truck new in Boise in August after my 1992 half ton's tranny went out on our summer vacation. It was an expensive vacation...LOL! It has the 6.0 automatic with 410 rearend and constantly got 14MPG on the freeway during break in. Didn't seem to matter how fast I drove, still got 14MPG plus a few tenths on our way to the Oregon coast.
    When I got back home here in Utah and went back to work I still got around 14MPG...then I put on new wheels and tires (265/75/16 BFG's)and the MPG dropped down to 13MPG. I haven't reprogramed the speedo yet so who knows what I'm really getting.
    I've got around 3600 miles on it so far and have been quite happy with it. No piston slap yet! New wheels and tires brought out the SHAKERADO big time but I just adjusted the tire pressure and if that don't work I'll head back for a rebalance.
    It's funny, the stock tires rode very nice. I didn't notice any shaking at all. The new tires and wheels just destroyed the ride but they look cool as hell so who cares.
    Sorry for the long post. It's my first, probably not my last.
  • obyoneobyone Member Posts: 7,841
  • abedulerabeduler Member Posts: 5
    I bought the same truck... I replace my tires with 265/75 R16's Mich. LTX M/S. Now the original tires were 245/75 R16's...Skinnier right? Same height? So it shouldn't change the mileage.

    fyi, I put a hard tonneau cover on and now can get 14.9 on the highway going 80mph. But Houston traffic in town lowers it b/t 12.8 and 13.5.

    Don't know what to tell you on the rough ride, my mich. drive pretty smooth.
  • zionalbinozionalbino Member Posts: 2
    I dropped the air pressure from 50psi down to 40psi and it really made a big difference with the shakes. I'm not sure why Discount Tires had the air pressure at 50, even though I guess you could go as much as 65psi, but by dropping it the truck settled down a bunch. My gas mileage might suffer a bit now but I'll take a smoother ride any time.
  • lariat1lariat1 Member Posts: 461
    A 245 75 16 tire is 30.5" and a 265 75 16 tire is 31.6' tall. that gives you about 4% difference so at 60mph you are actually around 63. Also a 265 tire is 20mm wider than a 245 tire. (the 3 digit number is the tread width).
  • kit1404kit1404 Member Posts: 124
    I know I am a Ford person on a Chevy website, but frankly I think your gas mileage is not good. My old, but in very good shape, F250 4X4, manual 5-speed OD and 460 cid engine gets a very reliable 12 to 13 mpg running around town. And, on the highway, she ain't much better but will pull close to 14 mpg just about no matter what it is hauling. This untouched engine has nearly 170,000 not all that easy miles on it. Would have thought things should be better by now. By the way, my 1999 F-150 with 5.4, auto, off-road 4X4 runs 80 mph all day long (not carrying much) and not uncommon also to see 18 mpg all day long. I live in New Mexico and these trucks run at an average of 6,500 foot altitude up and down long grades. Didn't intend to be trespassing on a Chevy site, just think our trucks should show some signs of better technology and somehow my F-150 feels like it has made some progress in the overall power/comfort/mpg wars.
  • ryanbabryanbab Member Posts: 7,240
    I seen my best milage when i was on a vacation this past summer in north carolina in the mountains. I almost hit 19mpg i couldnt believe it. my low has been 10.4 (i was in autotrac and 4 hi that month cause we got bombarded with snow)

    Also things to ponder

    Accessories like larger tires, grill guard, nerf bars, etc will add weight and also decrease your milage.
  • xyz71xyz71 Member Posts: 179
    in a 265 75 16 tire is not the width of the tread. It is the width of the tire at its widest point when it is installed on a wheel that is the measuring Rim Width for the tire.

    Go over to www.tirerack.com it explains it better than I can.
  • akjbmwakjbmw Member Posts: 231
    Variables and surprises.
    Went up to Wyoming for a week and got back Thursday night. Stayed in Jackson Hole and did our adventures from there.
    Two trips into Yellowstone. One was a 250 mile and the other was 340 mile.
    The surprise was the first trip got 19.6 mpg and the second was 19 even.
    The variables were the use of 91 octane for the climbing and the 45-50mph speeds in the park.
    The non-surprise was the just over 15 mpg on I-80
    coming back at 80-90mph.
    Truck is '98 K1500 ExtCab SB 5.7 AT 3.73 with shell and 265/75R16s.
    Great trip. Not ready to be back yet.
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